what i wonder is how the heck they are going to be able to pull off a sequal without invalidating the choices shepard made at the end of mass effect 3? because he made a pretty damn big one, and depending on factors in the sequal's story and setting, they might have to "canonize" one choice and invalitate the other ones.

i don't know if i can bring myself back into this series, it was a good story, but the story has ended. continuing on would likely would ruin it.

You know speaking of Mass Effect 4, I saw an article on IGN that Bioware states they will not be doing ME4. Besides that lets say they do. I would like to see a flash back to the Krogan Rebelions. You hear about it through out the series and it sounds so intense. You'd also still be able to see some of the characters we all know so well. For example Mordin with the STG and Wrex when he was young and killed his father. Maybe as well they could bring Matriarch Benezia into the picture somehow. She is more of a mystery then any other characters. Mostly, I want to see Wrex's story. As when Shepard spoke to Wrex in the first title his statement was "Story? There is no Story."

In a prequel set during the Krogan rebellions you would not have any Salarian characters that appeared in the original trilogy of games due to the fact that the rebellions occurred roughly 1500+ years before the first Mass Effect game and Salarians as a race have an average lifespan that is shorter than a humans and I'm yet to meet the human that has lived for a millennia and a half.

Mordin worked on the Genophage [i]Modification[i] project. Not the original Genophage. He was countering centuries of adaptations and alterations that had adversely affected the effectiveness of the Genophage in order to restore the status quo.